Добірка наукової літератури з теми "Giant gaseous planets"

ABSTRACT A gas giant planet which survives the giant branch stages of evolution at a distance of many au and then is subsequently perturbed sufficiently close to a white dwarf will experience orbital shrinkage and circularization due to star–planet tides. The circularization time-scale, when combined with a known white dwarf cooling age, can place coupled constraints on the scattering epoch as well as the active tidal mechanisms. Here, we explore this coupling across the entire plausible parameter phase space by computing orbit shrinkage and potential self-disruption due to chaotic f-mode excitation and heating in planets on orbits with eccentricities near unity, followed by weakly dissipative equilibrium tides. We find that chaotic f-mode evolution activates only for orbital pericentres which are within twice the white dwarf Roche radius, and easily restructures or destroys ice giants but not gas giants. This type of internal thermal destruction provides an additional potential source of white dwarf metal pollution. Subsequent tidal evolution for the surviving planets is dominated by non-chaotic equilibrium and dynamical tides which may be well-constrained by observations of giant planets around white dwarfs at early cooling ages.

AbstractPlanets typically are considerably more metal-rich than even the most metal-rich stars, one indication that planet formation must differ greatly from star formation. There is general agreement that terrestrial planets form by the collisional accumulation of solids composed of heavy elements in the inner regions of protoplanetary disks. Two competing mechanisms exist for the formation of giant planets, core accretion and disk instability, though hybrid combinations are possible as well. In core accretion, a higher metallicity in the protoplanetary disk leads directly to larger core masses and hence to more gas giant planets. Given the strong correlation of gas giant planets detected by Doppler spectroscopy with stellar metallicity, this has often been taken as proof that core accretion is the mechanism that forms giant planets. Recent work, however, implies that the formation of gas giants by disk instability can be enhanced by higher metallicities, though not as dramatically as for core accretion. In both scenarios, the ongoing accretion of planetesimals by gas giant protoplanets leads to strong enrichments of heavy elements in their gaseous envelopes. Both scenarios also imply that gas giant planets should have significant solid cores, raising questions for gas giant interior models without cores. Exoplanets with large inferred core masses seem likely to have formed by core accretion, while gas giants at distances beyond 20 AU seem more likely to have formed by disk instability. Given the wide variety of exoplanets found to date, it appears that both mechanisms are needed to explain the formation of the known population of giant planets.

Abstract Detections of molecules in the atmosphere of gas giant exoplanets allow us to investigate the physico-chemical properties of the atmospheres. Their inferred chemical composition is used as tracer of planet formation and evolution mechanisms. Currently, an increasing number of detections is showing a possible rich chemistry of the hotter gaseous planets, but whether this extends to cooler giants is still unknown. We observed four transits of WASP-80 b, a warm transiting giant planet orbiting a late-K dwarf star with the near-infrared GIANO-B spectrograph installed at the Telescopio Nazionale Galileo and performed high-resolution transmission spectroscopy analysis. We report the detection of several molecular species in its atmosphere. Combining the four nights and comparing our transmission spectrum to planetary atmosphere models containing the signature of individual molecules within the cross-correlation framework, we find the presence of H2O, CH4, NH3, and HCN with high significance, tentative detection of CO2, and inconclusive results for C2H2 and CO. A qualitative interpretation of these results, using physically motivated models, suggests an atmosphere consistent with solar composition and the presence of disequilibrium chemistry and we therefore recommend the inclusion of the latter in future modeling of sub-1000 K planets.

AbstractTerrestrial planets form in a series of dynamical steps from the solid component of circumstellar disks. First, km-sized planetesimals form likely via a combination of sticky collisions, turbulent concentration of solids, and gravitational collapse from micron-sized dust grains in the thin disk midplane. Second, planetesimals coalesce to form Moon- to Mars-sized protoplanets, also called “planetary embryos”. Finally, full-sized terrestrial planets accrete from protoplanets and planetesimals. This final stage of accretion lasts about 10-100 Myr and is strongly affected by gravitational perturbations from any gas giant planets, which are constrained to form more quickly, during the 1-10 Myr lifetime of the gaseous component of the disk. It is during this final stage that the bulk compositions and volatile (e.g., water) contents of terrestrial planets are set, depending on their feeding zones and the amount of radial mixing that occurs. The main factors that influence terrestrial planet formation are the mass and surface density profile of the disk, and the perturbations from giant planets and binary companions if they exist. Simple accretion models predicts that low-mass stars should form small, dry planets in their habitable zones. The migration of a giant planet through a disk of rocky bodies does not completely impede terrestrial planet growth. Rather, “hot Jupiter” systems are likely to also contain exterior, very water-rich Earth-like planets, and also “hot Earths”, very close-in rocky planets. Roughly one third of the known systems of extra-solar (giant) planets could allow a terrestrial planet to form in the habitable zone.

The discovery of gas giant planets around nearby stars has launched a new era in our understanding of the formation and evolution of planetary systems. However, none of the over four dozen companions detected to date strongly resembles Jupiter or Saturn: their inferred masses range from sub-Saturn-mass to 10 Jupiter-masses or more, while their orbits extend from periods of a few days to a few years. Given this situation, it seems prudent to re-examine mechanisms for gas giant planet formation. The two extreme cases are top-down or bottom-up. The latter is the core accretion mechanism, long favored for our Solar System, where a roughly 10 Earth-mass solid core forms by collisional accumulation of planetesimals, followed by hydrodynamic accretion of a gaseous envelope. The former is the long-discarded disk instability mechanism, where the protoplanetary disk forms self-gravitating, gaseous protoplanets through a gravitational instability of the gas, accompanied by settling and coagulation of dust grains to form solid cores. Both of these mechanisms have a number of advantages and disadvantages, making a purely theoretical choice between them difficult at present. Observations should be able to decide the dominant mechanism by dating the epoch of gas giant planet formation: core accretion requires more than a million years to form a Jupiter-mass planet, whereas disk instability is much more rapid.

We report the discovery of an extrasolar planetary system with two Saturnian planets around the star HD 83443. The new planetary system is unusual by more than one aspect, as it contains two very low–mass gaseous giant planets, both on very tight orbits. Among the planets detected so far, the inner planet has the smallest semi–major axis (0.038 AU) and period (2.985 days) whereas the outer planet is the lightest one with m2 sin i = 0.53 MSat. A preliminary dynamical study confirms the stability of the system.

AbstractTides come from the fact that different parts of a system do not fall in exactly the same way in a non-uniform gravity field. In the case of a protoplanetary disk perturbed by an orbiting, prograde protoplanet, the protoplanet tides raise a wake in the disk which causes the orbital elements of the planet to change over time. The most spectacular result of this process is a change in the protoplanet's semi-major axis, which can decrease by orders of magnitude on timescales shorter than the disk lifetime. This drift in the semi-major axis is called planetary migration. In a first part, we describe how the planet and disk exchange angular momentum and energy at the Lindblad and corotation resonances. Next we review the various types of planetary migration that have so far been contemplated: type I migration, which corresponds to low-mass planets (less than a few Earth masses) triggering a linear disk response; type II migration, which corresponds to massive planets (typically at least one Jupiter mass) that open up a gap in the disk; “runaway” or type III migration, which corresponds to sub-giant planets that orbit in massive disks; and stochastic or diffusive migration, which is the migration mode of low- or intermediate-mass planets embedded in turbulent disks. Lastly, we present some recent results in the field of planetary migration.

Giant planets migrate though the protoplanetary disc as they grow their solid core and attract their gaseous envelope. Previously, we have studied the growth and migration of an isolated planet in an evolving disc. Here, we generalise such models to include the mutual gravitational interaction between a high number of growing planetary bodies. We have investigated how the formation of planetary systems depends on the radial flux of pebbles through the protoplanetary disc and on the planet migration rate. Our N-body simulations confirm previous findings that Jupiter-like planets in orbits outside the water ice line originate from embryos starting out at 20–40 AU when using nominal type-I and type-II migration rates and a pebble flux of approximately 100–200 Earth masses per million years, enough to grow Jupiter within the lifetime of the solar nebula. The planetary embryos placed up to 30 AU migrate into the inner system (rP < 1AU). There they form super-Earths or hot and warm gas giants, producing systems that are inconsistent with the configuration of the solar system, but consistent with some exoplanetary systems. We also explored slower migration rates which allow the formation of gas giants from embryos originating from the 5–10 AU region, which are stranded exterior to 1 AU at the end of the gas-disc phase. These giant planets can also form in discs with lower pebbles fluxes (50–100 Earth masses per Myr). We identify a pebble flux threshold below which migration dominates and moves the planetary core to the inner disc, where the pebble isolation mass is too low for the planet to accrete gas efficiently. In our model, giant planet growth requires a sufficiently high pebble flux to enable growth to out-compete migration. An even higher pebble flux produces systems with multiple gas giants. We show that planetary embryos starting interior to 5 AU do not grow into gas giants, even if migration is slow and the pebble flux is large. These embryos instead grow to just a few Earth masses, the mass regime of super-Earths. This stunted growth is caused by the low pebble isolation mass in the inner disc and is therefore independent of the pebble flux. Additionally, we show that the long-term evolution of our formed planetary systems can naturally produce systems with inner super-Earths and outer gas giants as well as systems of giant planets on very eccentric orbits.

The large size and wide orbit of the recently announced exomoon candidate Kepler-1625b-i are hard to explain within traditional theories of satellite formation. We show that these properties can be reproduced if the satellite began as a circumstellar co-orbital body with the original core of the giant planet Kepler-1625b. This body was then drawn down into a circumplanetary orbit during the rapid accretion of the giant planet gaseous envelope, a process termed “pull-down capture.” Our numerical integrations demonstrate the stability of the original configuration and the capture process. In this model, the exomoon Kepler-1625b-i is the protocore of a giant planet that never accreted a substantial gas envelope. Different initial conditions can give rise to capture into other co-orbital configurations, motivating the search for Trojan-like companions to this and other giant planets.

Lors de cette thèse, je me suis attaché à améliorer notre connaissance des planètes géantes, depuis notre voisine Jupiter jusqu’aux exoplanètes lointaines : les Jupiter chauds. Grâce aux nouvelles observations gravitationnelles extrêmement fines du satellite Juno, entré en orbite autour de Jupiter en juillet 2016, il est possible d’améliorer significativement les modèles de structure interne de la planète. Cependant, cela ne peut se faire qu’à condition d’avoir une méthode suffisamment précise pour exploiter au maximum les données. J’ai donc étudié la méthode des sphéroides de Maclaurin concentriques et ses limitations. A l’aide des connaissances contemporaines sur les équations d’état, les propriétés diffusives et les transition ou séparation de phase entre l’Hydrogène et l’Hélium, il m’a alors été possible de produire de nouveaux modèles de Jupiter. Arriver à combiner les observations gravitationnelles de Juno et les abondances d’éléments observées par Galiléo n’a pu se faire qu’en décomposant Jupiter en au moins 4 zones, de l’enveloppe externe jusqu’au coeur compact. J’ai montré que la taille de ce coeur compact était dégénérée avec la variation d’entropie à l’intérieur de la planète.La structure interne des Jupiter chauds quant à elle est très dépendante de leur dynamique atmosphérique, qui entraîne une inflation de leur rayon. J’ai étudié les atmosphères de ces planètes à l’aide du modèle de circulation globale de l’Université d’Exeter et d’un code linéaire que j’ai développé, appelé ECLIPS3D. La caractéristique la plus importante de la circulation atmosphérique est la présence d’un jet superrotatif, étendu en latitude.J’ai donc étudié la création de ce jet à l’aide d’arguments théoriques pour s’assurer de sa pertinence physique. L’étude de la solution linéaire dépendante du temps, associée à des arguments numériques sur la convergence de quantité de mouvement par les vents verticaux m’ont permis d’établir une compréhension globale, cohérente de l’accélération de la superrotation dans l’atmosphère de ces planètes.Avec ce travail, j’ai amélioré ma compréhension théorique des planètes géantes et développé des codes qui peuvent être utilisés pour améliorer nos connaissances sur la structure interne et la dynamique atmosphérique des planètes géantes, que ce soit Jupiter, Saturne ou les Jupiter chauds
Through this thesis, I have been motivated by the will to improve our knowledge of giant planets, from our neigh- bouring Jupiter to the far away worlds across the galaxy: hot Jupiters.With the latest, extremely precise observations of the satellite Juno, new models of the interior of Jupiter can be derived. A precise enough method is required to take full advantage of these outstanding data, and I therefore studied the concentric Maclaurin spheroid method and its limitations.With contemporary understanding on the equations of state, diffusive properties and phase transition/separation of hydrogen and helium, I could then focus on producing new interior models of Jupiter. Combining the gravitational observations of Juno with the elemental observations of Galileo has proven to be a complicated task, which required to decompose the planet into at least four regions from the outer envelope to the inner, compact core. I have shown that the size of the compact core is degenerated with the entropy variation within the planet.Concerning hot Jupiters, I have reminded of the need to understand their atmospheric dynamics to constrain their interior structure, as the wind circulation can lead to an inflation of their radius. Studying numerically their at- mospheric dynamics was performed with the University of Exeter’s global circulation model as well as with the development of a linear solver that I called ECLIPS3D. An important, robust feature is the presence of a broad equatorial superrotation in the atmosphere of these planets.Finally, I have explored the spin up of this superrotation on theoretical grounds, to assess its physical relevance. I have calculated the linear time dependent solution to show the importance of differential drag and radiative damp- ing, and have used numerical simulations to highlight the importance of vertical momentum acceleration. Globally, a coherent picture of the initial spin up of superrotation was obtained.Through this work, I have improved my theoretical understanding of giant planets and developed various codes that can be used to study and improve our knowledge of the interior structure and atmospheric dynamics of giant planets, from Jupiter and Saturn to hot Jupiters

Context. For over 12 yr, we have carried out a precise radial velocity (RV) survey of a sample of 373 G- and K-giant stars using the Hamilton Echelle Spectrograph at the Lick Observatory. There are, among others, a number of multiple planetary systems in our sample as well as several planetary candidates in stellar binaries. Aims. We aim at detecting and characterizing substellar and stellar companions to the giant star HD 59686 A (HR 2877, HIP 36616). Methods. We obtained high-precision RV measurements of the star HD 59686 A. By fitting a Keplerian model to the periodic changes in the RVs, we can assess the nature of companions in the system. To distinguish between RV variations that are due to non-radial pulsation or stellar spots, we used infrared RVs taken with the CRIRES spectrograph at the Very Large Telescope. Additionally, to characterize the system in more detail, we obtained high-resolution images with LMIRCam at the Large Binocular Telescope. Results. We report the probable discovery of a giant planet with a mass of m(p) sin i = 6.92(-0.24)(+0.18) M-Jup orbiting at a(p) = 1.0860(-0.0007)(+0.0006) aufrom the giant star HD 59686 A. In addition to the planetary signal, we discovered an eccentric (e(B) = 0.729(-0.003)(+0.004)) binary companionwith a mass of m(B) sin i = 0.5296(-0.0008)(+0.0011) M-circle dot orbiting at a close separation from the giant primary with a semi-major axis of a(B) = 13.56(-0.14)(+0.18) au. Conclusions. The existence of the planet HD 59686 Ab in a tight eccentric binary system severely challenges standard giant planet formation theories and requires substantial improvements to such theories in tight binaries. Otherwise, alternative planet formation scenarios such as second-generation planets or dynamical interactions in an early phase of the system's lifetime need to be seriously considered to better understand the origin of this enigmatic planet.

The past decade has seen significant progress on the direct detection and characterization of young, self-luminous giant planets at wide orbital separations from their host stars. Some of these planets show evidence for disequilibrium processes like transport-induced quenching in their atmospheres; photochemistry may also be important, despite the large orbital distances. These disequilibrium chemical processes can alter the expected composition, spectral behavior, thermal structure, and cooling history of the planets, and can potentially confuse determinations of bulk elemental ratios, which provide important insights into planet-formation mechanisms. Using a thermo/photochemical kinetics and transport model, we investigate the extent to which disequilibrium chemistry affects the composition and spectra of directly imaged giant exoplanets. Results for specific "young Jupiters" such as HR 8799 b and 51 Eri b are presented, as are general trends as a function of planetary effective temperature, surface gravity, incident ultraviolet flux, and strength of deep atmospheric convection. We find that quenching is very important on young Jupiters, leading to CO/CH4 and N-2/NH3 ratios much greater than, and H2O mixing ratios a factor of a few less than, chemical-equilibrium predictions. Photochemistry can also be important on such planets, with CO2 and HCN being key photochemical products. Carbon dioxide becomes a major constituent when stratospheric temperatures are low and recycling of water via the H-2 + OH reaction becomes kinetically stifled. Young Jupiters with effective temperatures less than or similar to 700 K are in a particularly interesting photochemical regime that differs from both transiting hot Jupiters and our own solar-system giant planets.

We use a model of aerosol microphysics to investigate the impact of high-altitude photochemical aerosols on the transmission spectra and atmospheric properties of close-in exoplanets, such as HD 209458 b and HD 189733 b. The results depend strongly on the temperature profiles in the middle and upper atmospheres, which are poorly understood. Nevertheless, our model of HD 189733 b, based on the most recently inferred temperature profiles, produces an aerosol distribution that matches the observed transmission spectrum. We argue that the hotter temperature of HD 209458 b inhibits the production of high-altitude aerosols and leads to the appearance of a clearer atmosphere than on HD 189733 b. The aerosol distribution also depends on the particle composition, photochemical production, and atmospheric mixing. Due to degeneracies among these inputs, current data cannot constrain the aerosol properties in detail. Instead, our work highlights the role of different factors in controlling the aerosol distribution that will prove useful in understanding different observations, including those from future missions. For the atmospheric mixing efficiency suggested by general circulation models, we find that the aerosol particles are small (similar to nm) and probably spherical. We further conclude that a composition based on complex hydrocarbons (soots) is the most likely candidate to survive the high temperatures in hot-Jupiter atmospheres. Such particles would have a significant impact on the energy balance of HD 189733 b's atmosphere and should be incorporated in future studies of atmospheric structure. We also evaluate the contribution of external sources to photochemical aerosol formation and find that their spectral signature is not consistent with observations.

Ma thèse est consacrée à l'étude des atmosphères d'exoplanètes avec le télescope spatial James Webb Space Telescope (JWST). L'étude et la caractérisation d'atmosphères d'exoplanètes représente aujourd'hui un enjeu majeur au sein de la communauté scientifique et au-delà, puisqu'il s'agit de mettre en perspective tous ces mondes découverts au cours des trois dernières décennies et notre propre Système solaire, seul hôte connu de la vie à ce jour. La première partie de ce manuscrit est consacrée à une introduction qui présente l'état de l'art de notre connaissance des atmosphères d'exoplanètes en termes de composition atomique et moléculaire, de structure et de dynamique. Cette introduction se concentre sur l'étude des atmosphères d'exoplanètes dites transitantes (lorsque la planète passe devant ou derrière son étoile dans l'axe de visée des télescopes) et fournit une description de cette méthode observationnelle ainsi que des défis associés. La deuxième partie de ce manuscrit s'intéresse à l'élaboration de simulations d'observations d'atmosphères d'exoplanètes à l'aide du Mid-InfraRed Instrument (MIRI) du JWST (à l'époque encore en attente de son lancement) et de son spectromètre basse résolution (LRS). Mon objectif principal est la conception d'un outil de simulation complet et robuste qui permette à la communauté de valider les méthodes de réduction de données et de prédire les détections moléculaires [Dyrek+, sub., 2023, Morello, Dyrek+, 2022]. La troisième partie de ce manuscrit est dédiée à l'étude des performances en vol du LRS de MIRI après le lancement du JWST, le jour de Noël 2021. En effet, l'arrivée des premières données du JWST marque le début d'une étape cruciale de ma thèse. En particulier, je m'appuie sur le premier transit exoplanétaire observé par MIRI, celui de la Super-Terre L168-9b, choisie comme cible pour l'étude des performances. A partir de ces données, je me suis concentrée sur l'identification de variations instrumentales infimes qui pourraient porter atteinte à la stabilité temporelle des observations. De fait, je discute des axes d'améliorations des méthodes de réduction de données dans le cadre de l'étude d'exoplanètes en transit [Dyrek+, sub., 2023]. La dernière partie de ce manuscrit est consacrée à l'analyse scientifique des courbes de lumières photométriques et spectroscopiques d'atmosphères d'exoplanètes, des géantes gazeuses aux rocheuses tempérées. Je présente mes travaux collaboratifs dans le cadre du Temps Garanti d'Observation (GTO) et de l'Early Release Science (ERS) du JWST pour lesquels j'ai mené la réduction et l'analyse des données. En particulier, je m'intéresse à la super-Neptune WASP-107b dont l'analyse de données a conduit notamment à la première détection de dioxyde soufre (SO2) en infrarouge moyen et à la première détection de nuages de silicates [Dyrek+, sub., 2023b]. Enfin, je présente la première détection de l'émission thermique d'une exoplanète rocheuse et tempérée, TRAPPIST-1b, pour laquelle nous avons contraint la température de brillance qui indique l'absence d'une atmosphère dense [Greene +, 2023]. Le chapitre final est dédié à l'ensemble des perspectives ouvertes par la révolution observationnelle du JWST et de la future mission dédiée aux exoplanètes : Ariel
My thesis is devoted to the characterisation of exoplanet atmospheres with the newly-operating James Webb Space Telescope (JWST). Our understanding of exoplanet atmospheres is being revolutionised by the observational capabilities of such an observatory. The scientific outcomes will reach our scientific community and the general public, putting into perspective our knowledge of our own Solar System, the only system that is known to host life. The first part of this manuscript is devoted to an introduction that includes a state-of-the-art review of exoplanet atmospheres characterisation in terms of atomic and molecular composition, structure and dynamics. In this introduction, we focus on transiting exoplanets (when the planet passes in front of or behind its host star in the telescope's line of sight). We provide a description of this observational method and key results that have been obtained over the past two decades. The second part of this manuscript focuses on the molecular composition predictions with the JWST Mid-InfraRed Instrument (MIRI) and its Low-Resolution Spectrometer (LRS) that is meant to carry out atmospheric spectroscopy in an uncharted wavelength range. Here, we present realistic simulations of transiting exoplanets I developed during my thesis, with the MIRI LRS instrument that include various instrumental systematics likely to alter the atmospheric features we are meant to detect in our data [Dyrek+, sub., 2023, Morello, Dyrek+, 2022]. Our main objective is to design a comprehensive simulation tool that enables the community to build robust data reduction methods and to predict molecular detections. The third part of this manuscript is dedicated to the characterisation of the in-flight post-commissioning performances of the MIRI LRS. This work is based on the first exoplanetary transit observed with MIRI of the Super-Earth L168-9b, chosen to be a calibration target. My work focuses on identifying in-flight instrumental systematics that undermine observations' stability and more generally, the study of transiting exoplanets [Dyrek+, sub., 2023]. The final part of this manuscript is devoted to the scientific analysis of photometric and spectroscopic observations of both gas giants and temperate rocky exoplanet atmospheres. Here, I present my contribution on data reduction and analysis to the collaborative work we conducted as part of the Guaranteed Time Observation (GTO) and the Early Release Science (ERS) consortia. In particular, our work on the super-Neptune WASP-107b led to the first mid-infrared detection of sulphur dioxide (SO2) and silicate clouds [Dyrek+, sub., 2023b]. In addition, we conducted the first detection of the thermal emission of the rocky temperate exoplanet TRAPPIST-1b. In this work, we have constrained its brightness temperature, revealing key insights in the presence or not of an atmosphere [Greene+, 2023]. The final chapter of my thesis is dedicated to the prospects offered by JWST and the future Ariel mission, as these two telescopes will provide game-changing observations over the next decades

This is an advance summary of a forthcoming article in the Oxford Encyclopedia of Planetary Science. Please check back later for the full article.Although the second most abundant element in the cosmos is helium, noble gases are also called rare gases. The reason is that they are not abundant on terrestrial planets like our Earth, which is characterized by orders of magnitude depletion of—particularly light—noble gases when compared to the cosmic element abundance pattern. Indeed, such geochemical depletion and enrichment processes make noble gases so versatile concerning planetary formation and evolution: When our solar system formed, the first small grains started to adsorb small amounts of noble gases from the protosolar nebula, resulting in depletion of light He and Ne when compared to heavy noble gases Ar, Kr, and Xe: the so-called planetary type abundance pattern. Subsequent flash heating of the first small mm to cm-sized objects (chondrules and calcium, aluminum rich inclusions) resulted in further depletion, as well as heating—and occasionally differentiation—on small planetesimals, which were precursors of larger planets and which we still find in the asteroid belt today from where we get rocky fragments in form of meteorites. In most primitive meteorites, we even can find tiny rare grains that are older than our solar system and condensed billions of years ago in circumstellar atmospheres of, for example, red giant stars. These grains are characterized by nucleosynthetic anomalies and particularly identified by noble gases, for example, so-called s-process xenon.While planetesimals acquired a depleted noble gas component strongly fractionated in favor of heavy noble gases, the sun and also gas giants like Jupiter attracted a much larger amount of gas from the protosolar nebula by gravitational capture. This resulted in a cosmic or “solar type” abundance pattern, containing the full complement of light noble gases. Contrary to Jupiter or the sun, terrestrial planets accreted from planetesimals with only minor contributions from the protosolar nebula, which explains their high degree of depletion and basically “planetary” elemental abundance pattern. Indeed this depletion enables another tool to be applied in noble gas geo- and cosmochemistry: ingrowth of radiogenic nuclides. Due to heavy depletion of primordial nuclides like 36Ar and 130Xe, radiogenic ingrowth of 40Ar by 40K decay, 129Xe by 129I decay, or fission Xe from 238U or 244Pu decay are precisely measurable, and allow insight in the chronology of fractionation of lithophile parent nuclides and atmophile noble gas daughters, mainly caused by mantle degassing and formation of the atmosphere.Already the dominance of 40Ar in the terrestrial atmosphere allowed C. F v. Weizsäcker to conclude that most of the terrestrial atmosphere originated by degassing of the solid Earth, which is an ongoing process today at mid ocean ridges, where primordial helium leaves the lithosphere for the first time. Mantle degassing was much more massive in the past; in fact, most of the terrestrial atmosphere formed during the first 100 million years of Earth´s history, and was completed at about the same time when the terrestrial core formed and accretion was terminated by a giant impact that also formed our moon. However, before that time, somehow also tiny amounts of solar noble gases managed to find their way into the mantle, presumably by solar wind irradiation of small planetesimals or dust accreting to Earth. While the moon-forming impact likely dissipated the primordial atmosphere, today´s atmosphere originated by mantle degassing and a late veneer with asteroidal and possibly cometary contributions. As other atmophile elements behave similar to noble gases, they also trace the origin of major volatiles on Earth, for example, water, nitrogen, sulfur, and carbon.

The term "carbon cycle" is normally thought to mean those processes that govern the present-day transfer of carbon between life, the atmosphere, and the oceans. This book describes another carbon cycle, one which operates over millions of years and involves the transfer of carbon between rocks and the combination of life, the atmosphere, and the oceans. The weathering of silicate and carbonate rocks and ancient sedimentary organic matter (including recent, large-scale human-induced burning of fossil fuels), the burial of organic matter and carbonate minerals in sediments, and volcanic degassing of carbon dioxide contribute to this cycle. In The Phanerozoic Carbon Cycle, Robert Berner shows how carbon cycle models can be used to calculate levels of atmospheric CO2 and O2 over Phanerozoic time, the past 550 million years, and how results compare with independent methods. His analysis has implications for such disparate subjects as the evolution of land plants, the presence of giant ancient insects, the role of tectonics in paleoclimate, and the current debate over global warming and greenhouse gases

This chapter focuses on the giants of the solar system. Astronomers know somewhat less about the giant planets—except Jupiter—since no probes have gone down through their atmospheres and examined them directly. However, remote observations show that they have much in common with Jupiter. The low densities of all four giants mean they are mostly made of much lighter stuff than their terrestrial cousins. As on Jupiter, most of this bulk is gaseous in the outer layers but must be compressed into liquids in the interior. None of the giants has a solid surface, and the transition between gas and liquid is not a sharp one. Astronomers refer to the outer part of the fluid envelope as the atmosphere, although the depth of the base of the atmosphere is rather arbitrary.

Oxygen, in its molecular form, is the second most abundant gas in our atmosphere but second to none in courting controversy. Its discovery is often credited to the great experimenter Joseph Priestley (1733–1904), who in 1774 showed that heating red calyx of mercury (mercuric oxide) in a glass vessel by focusing sunlight with a hand lens produced a colourless, tasteless, odourless gas. Mice placed in vessels of the new ‘air’ lived longer than normal and candles burned brighter than usual. As Priestley noted in 1775, ‘on the 8th of this month I procured a mouse, and put it into a glass vessel containing two ounce measures of the air from my mercuric calcinations. Had it been common air, a full-grown mouse, as this was, would have lived in it about quarter of an hour. In this air, however, my mouse lived a full half hour.’ Later experiments revealed that mice actually lived about five times longer in the ‘new air’ than normal air, giving Priestley an early indication that air is about 20% oxygen. About the same time, the Swedish chemist Carl Scheele (1742–86), working in Uppsala, showed that air contained a mixture of two gases, one promoting burning (oxygen) and one retarding it (nitrogen). Like Priestley, Scheele had prepared samples of the gas that encouraged burning (‘fire air’) by heating mercuric oxide, and also by reacting nitric acid with potash and distilling the residue with sulfuric acid. However, by the time his findings were published in a book entitled the Chemical treatise on air and fire in 1777, news of Priestley’s discovery had already spread throughout Europe and the great English chemist lay claim to priority. Only later did it become clear from surviving notes and records that Scheele had beaten Priestley to it, producing oxygen at least two years earlier. The harsh lesson from history, which still rings true today, is that capitalizing on a new exciting discovery requires its expedient communication to your peers. The talented Scheele died at 43, his life shortened by working for much of the time with deadly poisons like gaseous hydrogen cyanide in poorly ventilated conditions.

The Galileo spacecraft, named after the Italian astronomer Galileo Galilei (1564–1642), who launched modern astronomy with his observations of the heavens in 1610, plunged to oblivion in Jupiter’s crushing atmosphere on 21 September 2003. Launched in 1989, it left behind a historic legacy that changed the way we view the solar system. Galileo’s mission was to study the planetary giant Jupiter and its satellites, four of which Galileo himself observed, to his surprise, moving as ‘stars’ around the planet from his garden in Pardu, Italy. En route, the spacecraft captured the first close-up images of an asteroid (Gaspra) and made direct observations of fragments of the comet Shoemaker–Levy 9 smashing into Jupiter. Most remarkable of all were the startling images of icebergs on the surface of Europa beamed backed in April 1997, after nearly eight years of solar system exploration. Icebergs suggested the existence of an extraterrestrial ocean, liquid water. To the rapt attention of the world’s press, NASA’s mission scientists commented that liquid water plus organic compounds already present on Europa, gave you ‘life within a billion years’. Whether this is the case is a moot point; water is essential for life on Earth as we know it, but this is no guarantee it is needed for life elsewhere in the Universe. Oceans may also exist beneath the barren rocky crusts of two other Galilean satellites, Callisto and Ganymede. Callisto and Ganymede probably maintain a liquid ocean thanks to the heat produced by natural radioactivity of their rocky interiors. Europa, though, lies much closer to Jupiter, and any liquid water could be maintained by heating due to gravitational forces that stretch and squeeze the planet in much the same way as Earth’s moon influences our tides. To reach Jupiter, Galileo required two slingshots (gravitational assists) around Earth and Venus. Gravitational assists accelerate the speed and adjust the trajectory of the spacecraft without it expending fuel. The planets doing the assisting pay the price with an imperceptible slowing in their speed of rotation. In Galileo’s case, the procedure fortuitously permitted close observations of Earth from space, allowing a control experiment in the search for extraterrestrial life, never before attempted.

It is convenient to distinguish two types of chemistry in the solar system. The first is thermochemical chemistry driven by the thermal energy of the atmosphere. This type of chemistry is important, for example, in the interior of the giant planets where pressures and temperatures exceed 1000 bar and 1000 K, respectively. The second type is disequilibrium chemistry, driven by an external energy source, of which solar radiation is the most important in the solar system. Chemical reactions between stable molecules are very slow at pressures less than 1 bar in planetary atmospheres. Sunlight is the ultimate source of greater chemical activity in the middle and upper atmospheres of planets. As shown in chapter 2, the absorption of solar ultraviolet radiation by atmospheric gases leads to the production of radical species (e.g., atoms, ions, excited molecules) that are extremely reactive. The bulk of atmospheric chemistry involves the reaction between the radicals themselves and between the radicals and stable molecules. In this chapter we briefly survey the chemical kinetics that are important for understanding the chemistry of planetary atmospheres.

Abstract The physical properties of the early solar nebula determined much of the subsequent course of terrestrial planet fonnation. A survey of the parameter space for three-dimensional ( 30) models of early phases of the solar nebula has been completed recently; the implications of these models for Earth formation are presented here. The models show that nebula evolution may have been dominated by angular momentum transport through gravitational torques, even during only mildly nonaxisymmetric phases, implying that the turbulent diffusion and mixing associated with viscous solar nebula models might be obviated. little or no evidence is found for planet fonnation through giant gaseous protoplanet instability; rather, Earth fonnation through planetesimal accumulation and impacts is indicated. Surface densities at 1 A.U. are typically quite adequate for Earth formation in a minimum mass ( -0.05 Mo) nebula The models also imply that the inner solar nebula may have been heated initially to temperatures on the order of 1500 K ( or even higher) through the compressional heating associated with nebula fonnation. Temperatures at 1 A.U. may have been regulated to values around 1500 K by a thermostatic effect produced by the vaporization of iron grains; the thermostatic effect minimizes the thermal gradient in the inner nebula and hence suppresses production ( through subsequent condensation) of a strong compositional gradient in the terrestrial planet region. A hot inner nebula is consistent with the gross depletion of volatiles on the Earth compared to solar abundances.

Forest management operations adequately integrated in the forestry value-chain are the gold standard in wildfire prevention. However, these operations generate considerable amounts of residual forest biomass (RFB) that cannot be legally disposed in land and further require suitable management. Residual biomass also includes highly flammable plants existing in the Portuguese forest such as gorse, broom, giant reed and acacia. Quite often wildfires in Portugal are linked with spreading of this residual biomass that promotes fuel accumulation. Besides deleterious impacts on rural and forestry economy, wildfires are also a driver for desertification and soil degradation. Alternative uses for this residual biomass to promote its valorisation and enable proper models of management of forest areas are needed, thus providing economic and environmental benefits towards decreasing of the fuel load. Though this biomass has reasonable carbon content and heating value, they also present inorganic composition (e.g. Na, K, Cl) that promotes operating problems in thermochemical conversion processes as combustion and gasification for useful energy production because of ash related problems (e.g., sintering/fouling), thus restricting their use in such applications. As such, biochar production by pyrolysis is a potential alternative to generate added-value. During pyrolysis the volatile matter of biomass is released to the gaseous phase, resulting a solid product, biochar, which is carbon-rich and contains most of the inorganics (nutrients) of the raw biomass. Exposure of biomass inorganics as free ashes is prevented in this process, and hence pyrolysis mitigates their negative effects. Nonetheless, the efficient pyrolysis of these types of biomass requires development of novel solutions optimized for energy and environmental performance. Enhancing of the energetic sustainability of the process and minimizing of the environmental impacts associated to the emission of gaseous pollutants are aspects of major relevance. Additionally, the biochar quality depends on biomass type, technology and operating conditions used. The BioValChar project (https://biovalchar.web.ua.pt/en/) seeks to answer these challenges related to valorisation of low-quality residual biomass through production of biochar by pyrolysis, which can return back to forest and rural soils. This approach will provide both carbon/nutrient cycling and synergies within forestry management, wildfire prevention, improvement of soil quality and rural development, under the circular economy principle. The research focus valorisation of residual forest biomass in full-control pyrolytic batch and continuous (auger-type reactor) processes, and testing of the resulting biochar performance as soil amendment. Moreover, a prototype of an integrated mobile unit for auto-thermal and continuous biochar production by pyrolysis of biomass is also being developed, by using the pyrolysis gases to provide the energetic needs of the process. Here we present the project overview, as well as some preliminary results on pyrolytic valorisation of one selected biomass (acacia) into biochar through distinct operating modes and conditions.

Optoacoustic spectroscopy has many advantages in the study of weakly absorbing gases, liquids, and solids. However, to date this capability has not been exploited for obtaining new spectroscopic information on interesting liquids and solids. In this paper I shall review the application of optoacoustic spectroscopy to cryogenic liquids and solids. Among the cryogenic liquid studies, overtone absorption spectra of liquid methane and ethane and those of solid hydrogens (H2, D2, and HD) are described in detail because of their importance to scientific understanding as well as to understanding of optical astronomical data of outer giant planets such as Jupiter, Uranus, and Neptune. In solid parahydrogen, I report the first observation of the fourth vibrational overtone (Δv = 5) in the 19,000-cm-1 region. Further, I describe the measurements of lifetimes of vibrational levels of solid hydrogen. These lifetimes are anomalously short for homonuclear diatomic molecules and provide a risk data for theoretical physics. I conclude by providing a view into the other profitable areas that can be explored through the study of weak absorption spectra.

The JUICE - JUpiter ICy moons Explorer – mission is the first large-class mission in ESA's Cosmic Vision 2015-2025 programme. Planned for launch in 2023 and arrival at Jupiter in 2031, it will spend at least three years making detailed observations of the giant gaseous planet Jupiter and three of its largest moons, Ganymede, Callisto and Europa, through more than 25 fly-bys and a final orbiting phase around Ganymede. Airbus Defence and Space Toulouse was selected as Prime Contractor in July 2015, and is responsible for the design and development of the AOCS Subsystem and the on-board Software. This paper focuses on the post CDR status of the JUICE AOCS HW and SW development and validation. Since the last JUICE presentation at the ESA GNC conference in 2017, AOCS equipment suppliers and Airbus, together with ESA, have made all efforts to progress on the development and qualification of AOCS HW and SW that best meet the demanding JUICE mission objectives and requirements. The major challenges encountered during this phase, and the solutions implemented by ADS and its partners, were in particular : •AOCS equipment enhancement of robustness to the jovian harsh radiation environment, and fulfillment of specific performance and autonomy needs of the JUICE mission : especially for the Star Tracker, the Inertial Measurement Unit, the Reaction Wheel and the Navigation Camera •Unique challenges posed on AOCS by a large Spacecraft with multiple flexible appendages, large propellant tanks and a main engine to be fired with large deployed solar arrays : main engine manoeuvres shaping, active damping loop of solar panels Out-Of-Plane flexible mode in safe mode, thrusters actuation frequency spreading. All these AOCS innovative solutions were successfully implemented and qualified through an intensive Monte-Carlo simulation campaign and functional testing with HW in-the-loop. In addition, coupled AOCS / CFD simulations have been performed in order to rule out any potential coupling issue between solar arrays flexible modes and liquid sloshing modes during critical mission phases neither in 0g nor in 1g conditions (namely the Emergency Damping Loop control in safe mode following a main engine thrust interruption). •Specific JUICE mission needs in navigation and science pointing accuracy, calling for vision-based autonomous navigation during jovian moons flybys, implemented through the EAGLE (for Enhanced Autonomous Guidance through Limb Extraction) on-board SW application. At the start of the prime contract with Airbus, EAGLE was a nice-to-have innovative concept still to be consolidated and promoted to convince mission authorities at ESA that it could really contribute to improve science return, and that it could be qualified for flight. Now a few years later, EAGLE is called by the ESOC CREMA, and EAGLE SW development and validation has been validated through closed-loop AOCS / Navigation performance simulations with Surrender virtual scene generation tool in-the-loop, as well as functional testing with HW in-the-loop. Even further, ESA has asked Airbus to complement EAGLE SW with an on-board estimation of the fly-by closest approach time-of-flight in order to better synchronize science payload instruments operations with the S/C relative trajectory. Available EAGLE validation results will be presented at the conference. •Specific JUICE mission needs in autonomy, calling for enhanced robustness to potential STR outages and autonomous resumption of critical insertion manoeuvres after safe mode : several specific SW functions have been developed to not only improve the AOCS robustness to STR outages which could result from the jovian harsh radiative environment, but also to minimize the probability of such STR outages, by assisting the STR for fast tracking recovery after a potential loss of tracking. Furthermore a major change in the overall JUICE FDIR strategy during mission-critical fail-operational phases was to replace an avionics warm-restart concept by a resume-after-safe-mode concept, proving more efficient to implement and validate. The final status of these enhanced-autonomy functions will be presented at the conference. •Non recurrent AOCS Software generation with Autocoding in a demanding ESA science SW product assurance environment : a lot of efforts have been spent to align the Airbus autocoding process with ESA SW PA expectations in a very constrained programmatic environment In addition to the above topics, if possible first results from orbit will be presented.